Wound toroidal core shell



1965 F. w. FASTNER ETAL 3,

WOUND TOROIDAL CORE SHELL Filed May 14, 1962 INVENTORS FRANK w. FASTNER RUDOLPH 0.8TOEHR 5 BY GLENN w. WAGNER ATTY.

United States Patent 3,210,701 WOUND TOROIDAL CORE SHELL Frank W. Fastner, Naperville, Rudolph 0. Stoehr, Des

Plaines, and Glenn W. Wagner, Westchester, lll., as-

siguors to Automatic Electric Laboratories, Inc., Northlake, 111., a corporation of Delaware Filed May 14, 1962, Ser. No. 194,388 2 Claims. (Cl. 336-96) This invention relates to encapsulated wound toroidal core assemblies, as for example loading coils, and more particularly to the construction of the potted shells therefor.

These assemblies are normally used in high voltage level applications such as in connection with voice transmission lines and therefore it is imperative to control the electrical and mechanical properties associated with them. Consequently, the design and encapsulation of these assemblies require the utmost consideration so that virtually no change occurrs in the coil operating parameters due to changes in temperature and humidity.

Accordingly the principal object of the invention is to provide a shell structure for the above type assembly which provides the latter with superior dielectric prop erties.

Another object of the invention is to provide a shell structure which when filled with an encapsulant is capable of withstanding momentary high-voltage pulses which may occur at times, for example, over the abovementioned transmission lines.

Another object of the invention is to provide a shell for a loading coil which has provisions for protecting and controlling the location of the splices of the lead out wires and the coil winding leads.

Still another object of the invention is to provide a shell structure whose design facilitates assembly of the wound toroidal core and whose cost of manufacture is kept at a minimum.

The invention features a toroidal core having high permeability characteristics around which is wound windings of the coil. In the case of the loading coil, for instance, there are two windings which are balanced inductively. The wound core has a rubber coating around it such as for example a silicon rubber which serves both as a moisture barrier and a resin barrier in its final assembly state. In addition, as a result of this coating, the coil is protected against mechanical shock that may be encountered during shipping or installation. Around the rubber coating is the potting compound or encapsulant and the corresponding shell. The potting compound more specifically is an epoxy casting resin which is a tough material not subject to resin-cracking and the entrance of moisture. The shell in addition to serving as an outer casing to the assembly serves as the structural means whereby the wound core can be completely enveloped by an encapsulant.

The shell is an integrally molded part made of a hard durable material such as for example styrene and is cupshaped having an open end. In the center of the base portion is a hollow post which extends through the wound core. To accommodate for variations in the inside diameter of the cores the post includes four thin splines which extend outwardly from the posts external surface. These splines assure a secure assembly between the wound core and the hollow post. Moreover, they permit the use of a thin wall for the center post and thus a post which is less subject to variations due to a change in hermetic conditions. This is in contrast to a solid center post or one having a thicker wall which tends to vary with a change in these conditions. Also by virtue of this design the epoxy casting resin can flow between the 3,216,701 Patented Oct. 5, 1965 center post and the inside diameter of the wound core thereby providing greater protection than with a solid post.

To carry out this feature still further the splines lead into further splines located along the base portion of the shell. These splines keep the core off the base of the shell so that the resin can also flow around the underside of the core between the base portion of the shell and the bottom side of the wound core.

The external shape of the shell is preferably round shaped except for a small portion which is virtually flat. In this flat portion are four countersunk holes through which lead out Wires are brought into the assembly during one of the assembly operations. These wires are placed along the inside surface of the walls and terminate at four shielding fingers. This shielding finger serves to locate and protect the splices made between the coil leads and the lead out wires. Heretofore, without the inclusion of the shielding fingers it was possible for the splices to contact the coil and short it out. This possibility is virtually eliminated with the instant design.

After the lead out wires are positioned in the shielding fingers the wound core is placed over the post and the shell is filled with the epoxy casting resin until the latter completely envelopes the wound core assembly and the shell is filled to the edge of the side walls.

After the resin is hard the assembly can be mounted either in a flat position by inserting a screw through the center post and securing it to a mounting board or it can, for example, be placed in a C-clamp in an upright position with the clamp secured to a mounting board. In the latter position a multi-coil unit can be formed by inserting a rod through the hollow of each assembly with a nut on each end.

It should be apparent that the cost of manufacture of the shell and the assembly in general is minimized by reason that the shell can be molded and envelopment of the core virtually automatic. Furthermore, no intricate operation is necessary with the device by virtue of the inclusion of the splices and shielding.

These and other objects and features of the invention will be more clearly understood upon carefully reading the following detailed description made with reference to the accompanying drawings of which:

FIG. 1 shows a perspective view showing a loading coil assembly having a pie shaped cross section cut therefrom.

FIG. 2 shows a plan view of the shell according to the invention.

FIG. 3 shows a side view of the shell including the four countersunk holes used to accommodate the lead out wires.

FIG. 4 shows a cross sectional view of the shell according to the invention taken substantially along the line 4-4.

Referring now to FIG. 1 of the drawings. The assembly includes ring core 10 which is made of a high permeability material such as for example molybdemum permalloy material. Around the core is wound coil 11 which comprises as in the case of a loading coil, two balanced windings which are enamel coated. Around the coil is a silicon rubber coating 22 which is supplied to the windings by a dipping operation, for example, to protect the coil from moisture and prevent the epoxy encapsulant from acting as a barrier to the windings and thus chance a change in the breakdown voltage characteristic of the assembly. Furthermore, the rubber coating 22 protects the wound core from mechanical shock that may be encountered during shipping or installation.

The rubber coated wound core is positioned within integrated shell structure 13 which is filled with an encapsulant 12. This encapsulant is preferably an epoxy casting resin which is not subject to resin-cracking and moisture penetration. Also this encapsulant provides a good bond with the shell 13. When epoxy resin 12 is in its liquid state it can freely flow around the Wound toroidal core assembly and thereby protects the latter from outside influences. This feature is principally attributed to the design of the shell hereafter described.

Referring now to FIGS. 2, 3 and 4, the shell 13 includes a hollow center post 17 which locates the wound coil and also enables the assembly when in its completed state to be mounted by placing a screw (not shown) in the hollow 23 and into a mounting plate, for instance. Extending from the center post is four slightly tapered radial splines 18 which assafore-mentioned assures securement of the coil 11 by extending against the silicon rubber coating of the coil. The inclusion of the splines 18 also permit the potting resin 12, to flow between the post 17 and the coil 11. At the base portion 21 of the shell, the four splines 18 form into ribs 19 that fan out and serve to raise the coil up. off the bottom of the shell. This feature furthermore enables the core to be enveloped by the epoxy resin material.

The shell wall 20 extends susbtantially in a circular pattern except for a flat portion 24 which contains four countersunk holes 14 which receive lead out wires 15 (FIG. 1). Lead out wires 15 are brought in through these holes and are placed along the inside surface of wall 20 terminating in shielding fingers 16.

Heretofore the wound toroidal core assemblies did not include specific provisions for the splices and thus their locations were not controlled with any degree of accuracy. This hindrance is removed according to the invention where the location and protection of the splice is positive by virtue of the inclusion of four shielding fingers 16. These four shielding fingers are made integral with the shell wall 20. They locate and receive the splices made between the lead out wires 15 and the coil leads (not shown). Each splice can be tucked back inside the corresponding shielding fingers and therefore be shielded from the coil. Moreover this feature lends itself to simple assembly operation and positive control of coil parameters. As in the case of the prior art these parameters were not always predictable and were subject to change due to environmental temperature changes and aging. Furthermore the particular design can be manufactured in minimum cost. This is attributed as aforementioned to the fact that the shell is an integral molded part but also to the fact that the shielding fingers 16 make it a simple operation to splice the lead out wires 5 What is claimed is:

1. In combination with an encapsulated wound toroidal shaped core having individually balanced coil windings spliced to leadout wires, and an outer surface, a shell structure comprising:

a flat base portion having a periphery and an aperture, said aperture being located within and concentric to said periphery;

a thin wall portion formed integrally with said base portion and projecting at right angles therefrom along said periphery,

a hollow post formed integrally with said base portion and positioned within said area definedby said wall portion, said hollow post being parallel to and concentric with said wall portion:

spline members integrally connected to said hollow post and extending radially thereform, said spline members projecting from, said hollow post toward said wall portion and having edges in contact with said surface of said core to space said core a distance from said hollow post and thereby enable an encapsulant to flow therebetween;

rib members integrally connected to and projecting outwardly from said base portion and being continuous with said spline members, said rib members having edges in contact with another portion of said surface of said core to space said core a distance from said base portion and thereby enable said encapsulant to flow therebetween; and means integrally connected to said. wall portion and extending toward said hollow post for receiving said splice and to space said core from said wall portion and thereby enable said encapsulant to flow therebetween; 2. A shell structure as claimed in claim 1 wherein said means comprises a plurality of L-shaped fingers which extend from said wall portion toward said hollow post, one portion of each finger being integrally connected to said wall portion and another portion being spaced from and extending parallel to said wall portion, said other portion defining a slot for reception of said splice and being in contact with still another portion of said surface of said core to space said core a distance from said wall portion and to enable said encapsulant to flow therebetween.

References Cited by the Examiner UNITED STATES PATENTS 2,695,856 11/54 Firth. 2,914,600 1l/59 Smith et a1. 336 -96 FOREIGN PATENTS 245,634 3/25 Great Britain.

JOHN F. BURNS, Primary Examiner.

JOHN P. WILDMAN, Examiner. 

1. IN COMBINATION WITH AN ENCAPSULATED WOUND TOROIDAL SHAPED CORE HAVING INDIVIDUALLY BALANCED COIL WINDINGS SPLICED TO LEADOUT WIRES, AND AN OUER SURFACE, A SHELL STRUCTURE COMPRISING: A FLAT BASE PORTION HAVING A PERIPHERY AND AN APERTURE, SAID APERTURE BEING LOCATED WITHIN AND CONCENTRIC TO SAID PERIPHERY; A THIN WALL PROTION FORMED INTEGRALLY WITH SAID BASE PORTION AND PROJECTING AT RIGHT ANGLES THEREFROM ALONG SAID PERIPHERY, A HOLLOW POST FORMED INTEGRALLY WITH SAID BASE PORTION AND POSITIONED WITHIN SAID AREA DEFINED BY SAID WALL PORTION, SAID HOLLOW POST BEING PARALLEL TO AND CONCENTRIC WITH SAID WALL PORTION: SPLINE MEMBERS INTEGRALLY CONNECTED TO SAID HOLLOW POST AND EXTENDING RADIALLY THEREFROM, SAID SPLINE MEMBERS PROJECTING FROM SAID HOLLOW POST TOWARD SAID WALL PORTION AND HAVING EDGES TO CONTACT WITH SAID SURFACE OF SAID CORE TO SPACE SAID CORE A DISTANCE FROM SAID HOLLOW POST AND THEREBY ENABLE AN ENCAPSULANT TO FLOW THEREBETWEEN: RIB MEMBERS INTEGRALLY CONNECTED TO AND PROJECTING OUTWARDLY FROM SAID BASE PORTION AND BEING CONTINUOUS WITH SAID SPLINE MEMBERS, SAID RIB MEMBERS HAVING EDGES IN CONTACT WITH ANOTHER PORTION OF SAID SURFACE OF SAID CORE TO SPACE SAID CORE A DISTANCE FROM SAID BASE PORTION AND THEREBY ENABLE SAID ENCAPSULANT TO FLOW THEREBETWEEN; AND MEANS INTEGRALLY CONNECTED TO SAID WALL PORTION AND EXTENDING TOWARD SAID HOLLOW POST FOR RECEIVING SAID SPLICE AND TO SPACE SAID CORE FROM SAID WALL PORTION AND THEREBY ENABLE SAID ENCAPSULANT TO FLOW THEREBETWEEN. 